The long-term objective of this project is a better understanding of the role of genetics in human behavioral disorders. Stuttering is being studied as a model trait because it is intrinsically interesting, it is a common disorder of children, and it is relatively easy to diagnose. Preliminary analyses using genetic models suggest a large genetic component, possibly even a single major locus, responsible for the disorder. As part of an ongoing study, data on over 550 families of stutterers (mostly adults) have been collected. We will extend this data base by studying families of children who stutter and children who have outgrown stuttering. We will also follow up children identified in our previous sample. These new studies will provide necessary comparative data to determine whether there is a genetic component to the difference between stuttering that is transient in childhood and stuttering that persists into adulthood. Genetic linkage studies and family studies of delayed auditory feedback will be done to better define the genotype(s) susceptible to stuttering.